Rear mounted turbos anyone!?!?

[longbow]

I remember reading about a Pug 205 in PPC a while back that has a bolt-on turbo at the rear and was working very well. Anyway, stumbled across this page:

http://www.balancemotorsport.co.uk/products.asp?su...

Strictly a low pressure set up, but on a Cerb that would probably get an easy 100hp extra. Not that I'm going to do it, but it makes you think..........

[stuthemong]

Mega lag on these setups though IIRC.

[nelly1]

Oi! No cheating before next Sunday...

[350Matt]

stuthemong said:

Mega lag on these setups though IIRC.

well theres the thing they don't have.

Its a bit counter intuitive but having the turbo a long way from the engine reduces the exhaust temps a lot which increases the density and the mass of the gas pushing the turbo, also the trick is to have a slightly undersized exhaust pipe so the build up f back pressure actually provides an surcharge of exhaust gas to spin the turbo up.

Ultimatly its not the best way to do a turbo installation but they do have their advantages.

[spitfire4v8]

Lag's only a problem if youre boosting a low compression engine. Using these systems to pep up a standardish spec car would be a great idea .. same performance as before off boost but with the added performance on boost. Also a big winner if you have a really crowded engine bay that won't like extra heat or you want to shift your performance add-on (extra weight) rearwards for RWD. Has anyone told dbv8 yet

[dirty boy]

spitfire4v8 said:

Lag's only a problem if youre boosting a low compression engine. Using these systems to pep up a standardish spec car would be a great idea .. same performance as before off boost but with the added performance on boost. Also a big winner if you have a really crowded engine bay that won't like extra heat or you want to shift your performance add-on (extra weight) rearwards for RWD. Has anyone told dbv8 yet

What about heat? Given the location of the fuel tank etc?

[RUSSELLM]

nelly1 said:

Oi! No cheating before next Sunday...

Funny seeing that, I've just been looking on the tomtom to see where I can get the BP102 fuel from on the way there.

If I can arrive empty at Milton Keynes on the way there, 100 miles to Ipswich..... Should leave me enough for a few runs.

How sad am I getting ?

[MackemPete]

RUSSELLM said:

Funny seeing that, I've just been looking on the tomtom to see where I can get the BP102 fuel from on the way there.

Does 102 make a noticable difference on mapped cars?

[cossiemetro]

no lag on these systems goto STS turbo's http://www.ststurbo.com/ they are excellent i've fitted a universal kit to my rwd rear engined fiesta makes for a very compact unit
my car needs mapping but look on the site at the corvette or 350z i'm sure your be convinced

[RUSSELLM]

MackemPete said:

RUSSELLM said:

Funny seeing that, I've just been looking on the tomtom to see where I can get the BP102 fuel from on the way there.

Does 102 make a noticable difference on mapped cars?

Thought the Cerb's ECU adjusted itself to suit ?

Probably wrong though

[SimonKD]

RUSSELLM said:

MackemPete said:

RUSSELLM said:

Funny seeing that, I've just been looking on the tomtom to see where I can get the BP102 fuel from on the way there.

Does 102 make a noticable difference on mapped cars?

Thought the Cerb's ECU adjusted itself to suit ?

Probably wrong though

Don't think so Russ, that's why Red Rose cars have the 95/97 octane button on the dash.

Regards
Simon

[RUSSELLM]

Doh

Probably going to put in anyhow.... If for no other reason, than to give myself a psychological advantage....

Over..erm... myself

[Redmist336]

350Matt said:

stuthemong said:

Mega lag on these setups though IIRC.

well theres the thing they don't have.

Its a bit counter intuitive but having the turbo a long way from the engine reduces the exhaust temps a lot which increases the density and the mass of the gas pushing the turbo, also the trick is to have a slightly undersized exhaust pipe so the build up f back pressure actually provides an surcharge of exhaust gas to spin the turbo up.

Ultimatly its not the best way to do a turbo installation but they do have their advantages.

I think you have been sold by marketing BS. The mass doesn't increase or decrease, what you do by cooling the air is increase density and decrease velocity. Cooler air may increase the life of the turbo, but as it's of lower velocity will increase spool times and decrease the amount of boost you can ultimately pull. Hence why race cars have the pipes before the turbo's lagged (if the metalurgy will withstand the heat).
Spool time is further increased by having the turbo further from the exhaust manifold. It's a self replicating system, intake air pressure = more exhaust = spool = greater intake pressure = ... The further apart you have these systems the more air there is to compress in both the exhaust and intake systems. Again why race cars try to have as small a volume pipework and intercooler as possible while balancing that with intake restriction and intake temps.

[Redmist336]

spitfire4v8 said:

Lag's only a problem if youre boosting a low compression engine. Using these systems to pep up a standardish spec car would be a great idea .. same performance as before off boost but with the added performance on boost. Also a big winner if you have a really crowded engine bay that won't like extra heat or you want to shift your performance add-on (extra weight) rearwards for RWD. Has anyone told dbv8 yet

Very true regarding compression ratios. Higher compression ratios mean considerably less lag and lower spool times. The problem is do you think that TVR got it wrong and that you can increase the dynamic compression ratio on the AGP further by adding boost? I think these systems will show some lag even with a stock CR. The distances between manifolds and turbos are just far too great. Saying that it's a half second or so of waiting from nutty power to insanely nutty power.

I've a Nissan 350z engine that runs two Garrett Turbos with stock CR. With clever plumbing, very short runs and small turbos you wouldn't notice that it's turboed (even though it's pulling just under 600hp with a massive spread of torque) I'm forced to run 100/110 Avgas in order to stop it from detonating. Thank god it's not running in an unleaded regulated motorsport.

[Boosted LS1]

Rear mount turbo's have been proved to work over in the US where they fit them to all sorts of cars. Some LS1's run in the 9's with this set up but they'll have been modded.

I take the point about compression though. If the engine's already got high compression and fairly feeble pistons then it won't be any good for boost beyond a couple of psi. If the pistons are cast hepolites I'd forget boost.

You may as well do it properly and fit forged pistons of a slightly lower compression.

[Redmist336]

I'd like to see proof of them working in a real world situation. Drag car's need controlled power from the start, building to max from there. I'd guess that any turbo system with large spool times would be perfectly suitable. It's the on/ off throttle situations where lag is really noticable. Given the tail happy nature of the Cerbera this might even be preferable. However it wouldn't be a car I'd like to drive. I like to know where my power is and that I have that power available instantly to pull me out of trouble.

[Billy_rfc]

This kit must be cheep compared to nirous to make it worthwhile cos the lag will be massive! I know the difference replacing a top mount intercooler to a front mount intercooler makes to lag and its noticeable, so this arrangement must be ridiculous. A convensional setup will mince meat this setup on every scale from power to drivability.

And I've just seen the price for the pug kit at £1457.50! Nitrous is a way better option.

Edited by Billy_rfc on Wednesday 5th August 11:39

[350Matt]

Pratical Performance car did a feature on a pug 205 with a rear mount turbo , I too was initially sceptical but they gave it a pretty positive report, bear in mind these kits sell pretty well in the states

[SXS]

If the turbo is the size of a washing machine and the pipes are like sewer pipes then PSI loss is inevitable, but lag is not so much an issue as many think.

The idea is to keep the turbo spooling efficiently, so sizing up the right turbo and pipework with your engine output is crucial. And also quite simply where the fu** one wants his power in the rev range.... smaller turbo will spool to higher rpms quicker than a big hairdryer...
Noble's cars have it bang on, plus they keep the high-lift cams too. TVR's could do with turbo upgrades... I'm surprised no ones yet looked into doing an off the shelf kit for them, but then you gotta worry about cooling and ste like that, the AJP aint the coolest running engine afterall, can-of-worms - needs to be opened... or you could just do what one of us did, buy a limited edition Z06 10.7 quarter miler and beef it up to 800 horses to 7 seconds was it?? lol

But as far as remote turbos - to be honest, unless you're a seasoned mad 'no brakes required' racer, you will hardly notice the lag alongside the V8 lag... lol
And like some have said, the US boys been doin this for ages, some pics I came across a few years back of a guy with a 15" turbo in the passenger seat literally.... lol

IMO
Its far less hassle increasing the compression and getting a sweetly tuned map in that cerbera brain. A few have shown that 440hp+ is not that hard to achieve with a bit of tinkerin.

[cptsideways]

We built one up on an MX5 in weekend, bar some technical (engineering & bodging) issues it worked, it was'nt laggy & worked surprisingly well !!

They are now known as Turboot's

http://www.driftworks.com/forum/drift-car-projects...

Edited by cptsideways on Wednesday 5th August 22:18